Method for isolating hydrocarbon-containing formations intersected by a well drilled for the purpose of producing hydrocarbons therethrough

Abstract

A method for isolating subterranean formations or zones intersected by a single wellbore is provided. The method comprises perforating a zone intersected by the wellbore and pumping a sealing means into the wellbore to seal against the side of the casing above and below the perforations to prevent communication from the zone into the wellbore after the casing has been perforated. The method further comprises fracturing the zone through the perforations prior to sealing and thus isolating the zone. Other zones thereabove are likewise perforated, fractured, sealed and thus isolated by pumping sealing means into the wellbore to seal the casing adjacent the perforations to prevent communication from the affected zones into the wellbore.

What is claimed is: 
     
       1. A method for isolating production zones in a wellbore having casing installed therein comprising: perforating said casing adjacent a first said production zone to communicate said first said production zone with said wellbore; and   pumping a first sealing means into said wellbore until said sealing means is adjacent said first production zone, to seal said wellbore at said first production zone, so that said first said production zone is isolated and communication between said wellbore and said production zone is prevented; and   wherein said first sealing means comprises at least one deformable ball having an undeformed diameter that is larger than an inner diameter of said casing.   
     
     
       2. The method of claim 1 further comprising: perforating said casing adjacent a second said production zone intersected by said wellbore to communicate said second said production zone with said wellbore, said second production zone being above said first said production zone.   
     
     
       3. The method of claim 2 further comprising: removing said first sealing means from said wellbore; and   allowing fluid from said first and said second said production zones to be communicated into said wellbore.   
     
     
       4. The method of claim 2 further comprising: pumping a second sealing means into said wellbore adjacent said second said production zone, to seal said wellbore at said production zone, so that said second said production zone is isolated and communication between said second said production zone and said wellbore is prevented by said second sealing means wherein said second sealing means comprises at least one deformable ball having an undeformed diameter that is larger than an inner diameter of said casing.   
     
     
       5. The method of claim 4 further comprising: perforating said casing adjacent a desired number of additional said production zones above said second said production zone to establish communication between said additional said production zones and said wellbore, said additional said production zones being located above said second said production zone;   pumping additional sealing means into said wellbore to seal said wellbore adjacent all of said desired number of said additional said production zones, wherein said casing is perforated and sealed at each of said additional said production zones in sequence from a lowermost additional zone to said uppermost additional zone, and wherein said pumping step is not performed on said uppermost zone so that said uppermost zone remains unsealed, each of said additional said zones being perforated and sealed prior to another of said additional said zones thereabove being perforated; and   wherein said additional sealing means comprises at least one deformable ball having an undeformed diameter that is larger than an inner diameter of said casing.   
     
     
       6. The method of claim 5 further comprising hydraulically fracturing selected of said first, said second and said additional said production zones prior to pumping corresponding sealing means into said wellbore to seal said selected production zones. 
     
     
       7. The method of claim 5 wherein each of said sealing means comprises a plurality of deformable balls having an undeformed diameter that is larger than an inner diameter of said casing. 
     
     
       8. The method of claim 5 further comprising removing said first, second and said additional sealing means from said wellbore and allowing fluid from said first, second and additional production zones to be communicated into said wellbore. 
     
     
       9. The method of claim 8 wherein said removing step comprises drilling through said sealing means so that each of said production zones are communicated with said wellbore. 
     
     
       10. The method of claim 2 further comprising displacing a fracturing fluid through said wellbore and into said first production zone prior to pumping said first sealing means downward in said wellbore to said first production zone. 
     
     
       11. The method of claim 2 wherein said sealing means comprises a plurality of elastically deformable balls, said balls having an undeformed diameter that is larger than an inner diameter of said casing. 
     
     
       12. The method of claim 11 wherein said elastically deformable balls are comprised of nitrile rubber. 
     
     
       13. A method of isolating hydrocarbon containing formations intersected by a wellbore drilled for the production of hydrocarbons therethrough, said wellbore having a casing installed therein, said method comprising: (a) perforating said casing adjacent a first of said formations to make perforations in said casing adjacent said first said formation and provide communication between said first said formation and said wellbore;   (b) placing a sealing means in said casing to seal against the side of said casing; and   (c) displacing said sealing means downwardly in said casing until said sealing means is adjacent said perforations, thereby sealing said casing adjacent said first said formation to prevent communication between said wellbore and said first said formations, wherein said sealing means comprises at least one deformable ball having an undeformed diameter that is larger than an inner diameter of said casing; and repeating steps (a), (b) and (c) for at least one other of said hydrocarbon-containing formations, in sequence from a lowermost of said other of said formations to an uppermost of said other of said formations until said casing has been perforated and sealed adjacent a desired number of formations, wherein only step (a) is performed on said uppermost of said other of said formations.     
     
     
       14. The method of claim 13 further comprising performing steps (b) and (c) on said uppermost of said other of said formations. 
     
     
       15. The method of claim 13 further comprising fracturing selected of said first and said other of said formations, wherein said fracturing step is performed prior to said displacing step. 
     
     
       16. The method of claim 13 wherein said fracturing step comprises forcing a proppant containing fracturing fluid into said selected of said first and said other of said formation zones through said perforations in said casing adjacent said selected formations prior to sealing said casing adjacent said selected formations. 
     
     
       17. The method of claim 13 wherein each said sealing means comprises a plurality of elastically deformable balls. 
     
     
       18. The method of claim 17 wherein said elastically deformable balls are comprised of nitrile rubber. 
     
     
       19. The method of claim 17 wherein said deformable balls in each said sealing means are stacked so that said balls seal said casing above and below the perforations made in said casing adjacent the corresponding said first and said at least one other of said formations. 
     
     
       20. The method of claim 13 further comprising removing said sealing means adjacent said first and said at least one other of said formations and communicating said formations with said wellbore. 
     
     
       21. The method of claim 20 wherein said removing step comprises drilling through said sealing means. 
     
     
       22. A method of fracturing and isolating production zones intersected by a wellbore having casing installed therein, comprising: (a) lowering a pressure-actuated perforating gun into said wellbore;   (b) hanging said perforating gun in said casing adjacent one of said production zones;   (c) filling said casing with a predetermined amount of fracturing fluid;   (d) positioning a sealing means in said casing above said predetermined amount of fracturing fluid;   (e) actuating said perforating gun to perforate said casing adjacent said one of said production zones, wherein said perforating gun automatically releases from said casing after said actuating step, and falls downward in said wellbore;   (f) fracturing said one of said zones with said predetermined amount of fracturing fluid; and   (g) sealing said casing adjacent said one of said zones with said sealing means to isolate said one of said zones and prevent communication therefrom into said wellbore.   
     
     
       23. The method of claim 22 wherein said actuating step comprises applying hydraulic pressure in said wellbore. 
     
     
       24. The method of claim 22 further comprising: (h) after step (g), lowering a perforating gun into said wellbore and positioning said perforating gun adjacent another of said production zones;   (i) perforating said another of said production zones;   (j) removing said sealing means from said wellbore; and   (k) allowing fluid from said one of said production zones and said another of said production zones to communicate with said wellbore.   
     
     
       25. The method of claim 22 further comprising repeating steps (a)-(g) for any number of zones from which production is desired intersected by said wellbore except wherein step (g) is not performed on an uppermost of said desired zones. 
     
     
       26. The method of claim 25 wherein said fracturing and said sealing steps comprises applying hydraulic pressure in said wellbore above said sealing means after said perforating gun is actuated, to force said fracturing fluid into said one of said production zones and said desired number of zones through the perforations in the casing adjacent each of said zones. 
     
     
       27. The method of claim 25 wherein step (g) is performed on said uppermost of said desired zones. 
     
     
       28. The method of claim 22 wherein said fracturing and said sealing steps comprises applying hydraulic pressure in said wellbore above said sealing means after said perforating gun is actuated, to force said fracturing fluid into said one of said production zones through the perforations in the casing adjacent said one of said production zones. 
     
     
       29. The method of claim 22, wherein said sealing means comprises a plurality of deformable balls, said deformable balls having an undeformed cross-sectional diameter greater than the diameter of the casing in the wellbore.